The chemistry of sediments at the Lower Aeolis Mons (Mt Sharp) from ChemCam/Curiosity observations

Nicolas Mangold1, Olivier Forni2, Diana L Blaney3, Ralph Milliken4, Marion Nachon5, Olivier Gasnault6, Martin FISK7, John P Grotzinger8, Joel Hurowitz9, Linda C Kah10, Laetitia Le Deit5, Stephane Le Mouelic11, Scott M McLennan12, Sylvestre Maurice13, Kathryn Stack3,8, Dawn Y Sumner14, Lucy M Thompson15, Roger C Wiens16 and MSL science team, (1)LPGN Laboratoire de Planétologie et Géodynamique de Nantes, Nantes Cedex 03, France, (2)Institut de Recherche en Astrophysique et Planétologie (IRAP), Toulouse, France, (3)Jet Propulsion Laboratory, Pasadena, CA, United States, (4)Brown University, Providence, United States, (5)University of Nantes, Nantes, France, (6)IRAP, CNRS, Université de Toulouse, UPS-OMP, Toulouse Cedex 4, France, (7)Oregon State Univ, Corvallis, OR, United States, (8)California Institute of Technology, Pasadena, CA, United States, (9)Stony Brook University, Geosciences, Stony Brook, NY, United States, (10)University of Tennessee, Department of Earth and Planetary Sciences, Knoxville, TN, United States, (11)CNRS, Paris Cedex 16, France, (12)Stony Brook University, Stony Brook, NY, United States, (13)IRAP, CNRS, Université de Toulouse, UPS-OMP, Toulouse, France, (14)University of California, Davis, Earth and Planetary Sciences, Davis, United States, (15)University of New Brunswick, Fredericton, NB, Canada, (16)Space Science and Applications, Los Alamos, United States

Contact First Author: Nicolas Mangold; nicolas.mangold@univ-nantes.fr

Abstract ID#: 34220

 

English Abstract:
The Curiosity rover has encountered a diversity of sedimentary rocks, which overall have displayed significant variations in both texture and composition. Early observations by the Curiosity rover in Gale crater revealed isolated outcrops of cemented pebbles and sand grains with textures typical of fluvial sedimentary conglomerates (Williams et al., Science, 2013). Conglomerates observed by Curiosity contain clasts with a strong diversity in albedo and textures indicating multiple sources on the Gale crater rims. Sandstones and mudstones observed at Yellowknife Bay were interpreted as having been deposited in a fluvio-lacustrine environment (Grotzinger et al., 2014). More stratified sandstones have been observed in the second and third terrestrial years of investigation in the outcrops named Cooperstown, Kimberley, and Pahrump. The latter outcrop corresponds to the lower Mt Sharp/Aeolis Mons based on orbital images and its facies is interpreted as fluvio-lacustrine sediments (Sumner et al., this meeting). The Pahrump sediments have major elements chemistry close to that of the conglomerates, suggesting a genetic relationship through the deposition of fluvial sediments from a similar source, likely the Gale crater rim. Pahrump sediments display subtle variations in major elements connected to variations in facies. There is an enhanced Mg content in resistant layers, which is correlated with a depletion in Fe and enhanced Al/Si ratios as well as enhanced hydrogen emission. These resistant layers have also a higher CIA (Chemical Index of Alteration) compared to the sediments previously encountered. These observations point towards the role of alteration during deposition and/or diagenesis during cementation in these sediments. Diagenesis did leave its imprint to these sediments as seen from the presence of cm-scale dendritic concretions, often enriched in Mg, S and Ni, suggesting fluid circulation during burial. Light-toned veins, observed as being calcium sulfates, postdate layers cementation as well as all other diagenetic features. In summary, Pahrump outcrop exhibits layers with a multiple role of water from the deposition of sediments in a fluvio-lacustrine system to their alteration and diagenetic evolution pointing towards a complex evolution in a climate warmer than the present one.
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